


A Kinder World, After Dark

by Last_Haven



Series: Another World [3]
Category: Undertale (Video Game)
Genre: AFAB Frisk, Adult Frisk, Alternate Universe - Underfell, Flirty Frisk, Grinding, Nonbinary Frisk, Other, Plot What Plot/Porn Without Plot, UT!Frisk in Underfell, Underfell Sans, might add new chapters as time goes on
Language: English
Status: Completed
Published: 2017-12-25
Updated: 2017-12-25
Packaged: 2019-02-20 10:51:35
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,380
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13145118
Author URL: https://archiveofourown.org/users/Last_Haven/pseuds/Last_Haven
Summary: Set in the same universe as The World, Upside Down and Making a Kinder World, specifically during Making a Kinder World--would recommend reading The World, Upside Down at least first, although you could technically read this alone. A classic Undertale!Frisk was transported to an Underfell universe and set out to free monsters as they had in their youth. After the Barrier fell, Frisk and Sans now live in the same household.One night, the two decide to play strip poker. Sans has his objections to how they're playing; Frisk is determined to flirt at every step of the way.





	A Kinder World, After Dark

            “So, are you going to actually play right, or are you going to keep letting me win?”

            Frisk paused, glancing up to look at Sans. He was still busy arranging his cards; Frisk hadn’t even had a chance to pick up their own cards yet after they had dealt both of their hands. “I have no idea what you mean,” they quipped, grinning already.

            He refused to look up at them, laser focused on his cards. “I mean we’ve only played two hands and not only did you purposefully toss out good cards, you immediately took off both your shirt and binder first despite the fact that could have gone for, oh, your socks or your belt.”

            It was getting difficult not to giggle at him. “Maybe I didn’t want my feet to get cold or have my pants drift down. Plumber’s butt crack isn’t sexy, you know.”

            That got him to pause; shutting his eyes, he raised his head to stare at the ceiling before lowering his gaze back down to their face. “Are you insinuating that you’re trying to look sexy in front of me?”

            “That depends.” They gave in and grinned. “Is it working?”

            The corners of his mouth twitched as he closed his eyes and turned his head down before opening them again. “You are a nightmare. Deuce’s wild.”

            “Oh, come on,” they tried desperately to keep their tone even as they pulled out one of their cards, discarded it, and got a new one. Oh. Maybe they wouldn’t throw this hand—they had a full house now. “I was under the impression you liked my—what did you call them? Squishy bits.”

            For a moment, Sans hid behind his cards before he sighed and lifted his face up although his cheekbones were still stained red. “You are never going to let that go.”

            “Well, considering _you_ didn’t want to let go of my tits that morning, I’d say we’re pretty alike. Are you holding or what?”

            He grumbled about something, the red on his face spreading farther as he discarded one card; they dealt him a new one. His poker face was excellent—they had no idea what he had now or not. “I apologized already.”

            They flatly laughed. “I said I didn’t mind. It was just really funny listening to you, half asleep, trying to argue that my chest made a better pillow than your actual one.”

            “Fuck you. And you didn’t answer my question.”

            They made a show of looking at their hand before tossing some poker chips onto the pile besides them and then looking back up at him. “Five hundred. And for your information, I am not just letting you win.”

            He narrowed his eye sockets at the chip pile before grabbing some chips of his own to meet the bet. “Is that a fact?”

            “It is.” They tossed their hand down, faces up.

            He snorted and tossed his hand down as well, face up. Four nines.

            Damn. They’d lost fairly on that one, but from his cautious look, he seemed to think they still might have thrown the hand on purpose—well, let him think that. It’d keep him guessing. “Well, that does give me an excuse to take my belt off.”

            He rolled his eyes and collected the cards to shuffle them. “A likely story.”

            They had to catch themselves from giggling again as they tossed their belt aside. “Believe what you want. You don’t have to worry about your belt digging into your gut. _I_ do.”

            “Your gut’s fine. Ante up. Deuce’s still wild.”

            They decided instantly that no matter what their cards were, they were going to lose on purpose, just to take off their pants and fluster him more. “Says the asshole who can literally drop half his weight just by taking off his clothes. I still don’t get how that works.” They pitched in the chips and then checked their hand he dealt them; two red threes, the six of spades, four of diamonds, and eight of clubs. Colorful. They tossed out one of their threes; he dealt them a two of hearts. Perfect.

            He chuckled, sorting through his cards, and getting new ones before he tossed his bet in. “I told you. The aura of skeletons’ magic fills the clothes out. That’s all there is to it.”

            “That doesn’t explain why your _weight_ changes.” They decided against raising the bet and instead tossed in their share.

            “Magic,” he answered primly before tossing down his cards. He had a pair of aces.

            They hid a smirk as they laid down their losing hand before slipping off the bed. Turning their back to him—as if he thought they couldn’t see, he couldn’t help but peek like a naughty child—they unzipped their pants and made a show of sliding them off, sensually. Once they stepped out of the pant legs, they slipped back onto the bed. “My turn to deal already?”

            “Babe,” he began, voice tight—he had his face behind his palm, as if it would hide the blush that now coated his face or the way he was squirming. “Why aren’t you wearing underwear?”

            Honestly, they just hadn’t wanted to put them on after they showered earlier. Still, they weren’t going to say that to him. “Visible panty lines.”

            The sheer audacity made him look up, which meant he caught an eye full as they purposefully sat cross legged. After a moment, he forced his gaze up to their face. “You were wearing baggy pants,” he forced out.

            They beamed sweetly. “I had to be sure, love. Now, ante up.”

            “Frisk,” he managed, voice shaking. “You don’t have anything else to lose.”

            They grinned. “That’s not true,” they chirped and then leaned back so they could hold up one stocking clad foot in the air. “I still got my socks.”

            Hilariously, it was the socks that made Sans gulp loudly, his gaze fixed on their foot as they wiggled their toes and rotated their foot. They would have teased him about having a foot—or at least a sock—fetish, if his gazed hadn’t immediately followed the line of their leg straight down to the crux of their legs.

            Socks—the gateway to sexiness for monsters, apparently. That was another thing they still didn’t get, but at least they could _kinda_ see the appeal.

            To his credit, he forced his gaze away, even though his face was now practically glowing with the blush. “When did you get that tattoo anyway?”

            Frisk paused, crossing their legs again. “What, the one on my back?”

            He huffed as he picked up the deck and began to shuffle again. “Do you have any other ones?”

            “Nah. I had been thinking about getting more, but uh, then I came here and I’m not entirely sure I would get to keep any tattoo I get from now on.” Rather than let that awkward admission hang in the air—their body seemed to be trapped in time and any changes made quickly vanished back to how they’d been when they first arrived in this world—they cleared their throat. “I got it a year before I came, actually. I met a guy who was a tattoo artist and he needed guinea pigs for his portfolio. He jumped at the chance to work on a famous person.” They paused, biting their lip to keep from laughing. “Are you, uh, going to deal or…?”

            He shuffled again. “Just being thorough.” Finally, he began to deal cards. “Why the bones and flowers though?”

            On their back was an anatomically correct ribcage, as seen from the back. Cracks ran down the vertebra and a few of the ribs were broken, allowing a better view of some of the red and gold marigolds that grew inside the bones and twined around the spinal column. “He actually needed more practice on bones specifically and with my fucked up rib I thought it’d be kinda funny. Funny story about the flowers, though.” They tossed their ante in and checked their cards. It was a shit hand; they were instantly pleased and set them face down. “He screwed up one of the cracks and needed to hide it. I suggested the marigolds. We went from there. I’m holding, by the way.”

            He grunted, eyes focused on the cards as he tossed in his own chips and arranged his cards. “Why marigolds?”

            They raised their bet just to be coy. “I like marigolds.” They smiled softly. “They’re my favorite.”

            “Are they? Cards up.” When he saw their cards, he glared at them. “Why do I even play with you?”

            They ignored their second question and instead straightened one leg. Grabbing one sock by the toe, they pulled it off and dropped it onto the pile; when they looked at Sans they found he’d finally given in and was openly gawking at them, face hungry. They smirked. “They _are_ my favorite, actually. So, Sans,” they reached out and took the cards, starting to shuffle—he was so busy staring at their, well, _everything_ , that he didn’t even notice that they had started to stack the deck. “How about a proposition?”

            He grunted, eyes drifting down from their chest to the thick thatch of hair that ran from under their bellybutton down, down, down. He was good—the motion almost looked like he was actually following their hands as they set them in their lap. Finally, he cleared his throat. “I’m listening.”

            “One last hand, winner takes all.”

            He blinked as if he was coming back to himself and finally glanced up at them. “Huh?” Figures—he _would_ only pay attention once they proposed a wager.

            “If I win, I get to ride you.” They smiled, the soul of innocence. “If you win, you get to decide whatever position you want.”

            The noise he made sounded like his mind had gone flying off its tracks and into somewhere downright obscene. He finally blinked and sat up. “Deal the cards.”

            “Is that a yes?”

            “Deal the fucking cards.”

            Smiling sweetly, they dealt the cards. He nearly tossed his ante at them, picking up some new cards—interestingly, they easily read the delight in his face. The skeleton wasn’t even trying to hide it. Frisk discarded one card and picked up the one they had placed specifically for this. Rearranging the cards, they put in their bet and he tossed in his.

            He put his hands down. Another four of a kind, a set of eights. He grinned.

            They allowed themselves only the slightest smile as they set their cards down. Ace, King, Queen, Jack, Ten, all hearts.

            He blinked. “Oh,” he managed after a moment. Without another word, he shoved the chips and cards off the bed and reached for them. “Well, honestly, I didn’t really lose.”

            With a knowing laugh, they pulled off their last sock and crawled into his lap.

            The moment they were took their seat, his hands were drawn, like a compass to true north, straight to their ass. They couldn’t stop their amused giggle, but their attention quickly shifted as they reached for his face. The consistency of his skull never failed to bemuse them—it was firmer than flesh, less flexible than rubber, but still far more pliant than human bones and it was warm to the touch. Oddly, his teeth were very human like despite their size.

            It was funny—like human teeth, Sans couldn’t feel much of anything from them, but you wouldn’t know that if you happened to see his face at those moments. His attention flickered and the lights of his eyes went out at the first touch of their tongue against a canine. He asked them once while they liked playing with his teeth like this, but they hadn’t thought he’d much care for the truth. These were the teeth that had torn into their shoulder like it was little more than a hamburger, snapped their collarbone like a twig—his jaw pressure _had_ to be comparable to a human’s if not greater. And yet, here he was, his entire head still for them, letting them do whatever they wanted—they could cut their tongue open with a single careless twist, but it wouldn’t be because he’d moved. There was something about power there, something like an adrenaline high like they used to get when they did something reckless. Something about making yourself vulnerable, but knowing that there was no real danger.

            That, however, sounded kinda bad, so they just told him that it was because he made the most exquisite noises when they lapped at his mouth. Which was still true, and it meant they got to see his skull turn this interesting shade of red.

            They were still tracing the jagged edge of a tooth as his hands began to wander; one drifted upward, following the line of the knobs of their spine, tracing each curve and dip on the way up. Despite his admitted preference to the thicker parts of their flesh, they could understand his fascination with the parts of their body that he could easily see their bones. Did the flesh over their bones look to him like a scantily dressed human did to other humans—tempting partially because you just wanted to know what that body looked like underneath the layers? His exploration ended at the base of their head for a moment, cupping the curve of their neck.

            His other hand, however, was busy heading the opposite way.

            They rose up to give him more access as his hand continued downward and then it was their turn to make a needy noise as his fingers slipped down and down. They paused and let their head roll back as their breath hitched in their chest and they tried not start grinding down.

            “Careful,” they murmured as his fingers circled sensitive skin. They forced themselves to pull their head back down—they loved looking at him when his eyes filled with desperation. They tried to extend him the same courtesy; judging by his smirk, he appreciated the look in their face. “You’re— _ah_ —going to need gloves if you want to play there.”

            He snorted at that—there’d once been a _very_ awkward moment when the tip of one of his fingers got—to put it delicately—separated from the rest of his finger when he had to jerk his hand back. After a small interruption—someone had banged on the wall to encourage them to keep it down—there had been a real awkward but funny moment when he had to figure out a way to find and draw it back out from their body. Luckily, the segment snapped back into place the moment he got the rest of his finger close enough; they’d been a little over stimulated by then, but they’d still been laughing about it.

            Still, no need to repeat that experience. They still had nightmares where they had to go to the hospital and look a doctor dead in the face and say that they had finger bones in their body in places bones were just not meant to go and for _exactly_ the reason someone would assume.

            Behind them, they heard the scrape of the nightstand’s drawer opening as Sans manipulated it with his magic, finally letting go of their neck to snatch whatever it was he summoned. Using his moment of distraction, they ground down onto his lap and hand.

            “Fuck,” he muttered as they pressed downward, his eyes sliding shut.

            “Sans, my dear,” they huffed a laugh. “I believe you’re a bit overdressed for the occasion.”

            “Can’t have that,” he managed tightly.

            With a grin, they grabbed his shoulders and pressed him down onto his back before reaching down to undo his pants. He took a moment to draw back his hand from their skin to help them by tugging at his fly while they undid his belt. Once he was free, they helped him shuck off his pants as he lifted his hips up. Rather than give him a moment to catch himself though, as soon as he kicked his feet free, they lined themselves up and rolled their hips straight against his, rubbing right against his pubic crest.

            Choking off a curse, he grabbed their hips. Not to stop them, but draw them closer as they moved. They grinned down at him as he bucked up against them. “Turnabout’s fair play, love.”

            “One day,” he grunted, trying to match their pace, “I’m going to chain you to a goddamn wall and then we’ll see who’s calling the shots.”

            “Mm, I told you, handsome, you gotta pick out a safe word first then I— _ah!”_ They nearly faltered when they felt warm, slick fingers slip inside them. So that’s what he was getting out: lube and some vinyl gloves. “T-then when can play.”

            He didn’t bother to reply as he twisted his fingers and then crooked them. Their breath stuttered and they nearly lost themselves to the pleasure.

            Their speed picked up after that, his fingers drawing them further on until it was all they could do to fist their hands into his sweater and press their face into the bed besides his to try to muffle the moans and choked off whimpers. When he called their name, made them turn to look at his face—their gazes met and he looked as lost as they did. They hit a fevered pitch and

            _(warm, warm, so warm and deep)_

            Tension winding like a spring and

            _(this is safe, you are safe, I am here and we are)_

            He called their name and they are

            _(tumbling down, come, come, it is safe here in the dark place in between)_

            They ride out their orgasm, coaxing their hips to keep moving until they finally heard his breath come short and stuttered and his body went limp. Stroking the curve of his skull, they kissed the side of his face until he shifted and gave them more access to the rest of his face. They pressed kiss after kiss to it until he at last he wound his arms around them and pulled them down until every inch of them met.

            Carefully, they slipped their arm under his head, cradling it as they kissed his teeth carelessly. He wouldn’t let go of them—not for a while, so they instead used their free arm to tug the sides of the blanket up around the two of them. They did their best to tuck themselves up in the folds.

            Finally, his shivers subsided and their blood stopped racing in their ears. Once that happened, they gently freed themselves, ignoring his wordless protests as they tugged him up to the head of the bed. “Come on, sleepy,” they teased, hauling him up. “Don’t you want to use your own pillow?”

            “I’d settle for your gut,” he replied with surprisingly clarity. Still, he yanked off the used glove and tossed it in the direction of the trashcan—hopefully, they’d remember to grab it tomorrow. One time they’d forgotten to take care of one and had to chase one of the cats around, trying to get it back before Papyrus spotted them and questioned them how his cat got a hold of it.

            They snorted at him and kept tugging until he was finally in place. Once he was, they reached down and hauled the blanket up again. Quickly, they slipped back underneath it and crawled closer to him. Next to them, his breath was already evening out and his eyes were clasped shut. Smiling, they prodded his right cheekbone. When he groaned at them, they chuckled. “See? This is why you play cards with me.”

            “You stacked the deck,” he mumbled, barely conscious.

            They grinned. “And you count cards. Isn’t it all fair in the end?”

            “When the game ends like that, yeah.”

            “So that means we should play more often,” they teased, tucking their head against his.

            One of his hands reached up to clasp the arm they tossed across his chest. “Next time, we’re playing euchre.”

            They snorted, but by the time they’d thought of a retort, he’d already fallen asleep. Still amused, they gave in and drifted off as well.

**Author's Note:**

> Merry Christmas! This was a Christmas bonus for my readers of Making a Kinder World. I might continue adding more chapters to this if I feel so inclined, but as it stands, this is a complete story.


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